JP2011230526A - Walkie forklift - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a walkie forklift in which an axle load of a drive wheel can be reduced when the forklift is lightly loaded while preventing the drive wheel from being slipped.SOLUTION: The walkie forklift 1 includes: a spring member 15 energizing a drive wheel suspension mechanism 11, 12 downward with respect to the frame 4 of a vehicle body 3; an expansion and contracting member 14 disposed between the end of the spring member 15 and the frame 4 or between the end of the spring member 15 and the drive wheel suspension mechanism 11, 12; a slip detecting unit 31 detecting the slip of the drive wheel 7; and a control unit 32 that stretches the expansion and contracting member 14 when the slip is detected by the slip detecting unit 31 and an energizing force by the spring member 15 is increased.

Description

  The present invention relates to a walkie forklift that a driver who holds a steering handle controls while walking.

  As a conventional walkie forklift, the one shown in FIG. 6 is known (see, for example, Patent Document 1). As shown in the figure, a conventional walkie forklift 100 is attached to the front of the vehicle main body 3, a battery storage portion 5 that moves up and down as the lift cylinder 16 in the vehicle main body 3 expands and contracts, and the battery storage portion 5. A pair of left and right forks 6 and a steering handle 2 attached to the upper portion of the vehicle body 3 so as to be turnable are provided. A drive wheel 7 suspended by a drive wheel suspension mechanism and a pair of caster wheels 8 disposed on the left and right sides of the vehicle body 3 are provided at the lower portion of the vehicle body 3. A wheel 9 is provided. The own weight of the walkie forklift 100 and the load of the load loaded on the fork 6 are carried by the drive wheel 7, the caster wheel 8 and the load wheel 9.

  The drive wheel suspension mechanism includes a bearing mechanism 11 that can be moved up and down with respect to the frame 4 of the vehicle body 3 by a link mechanism 13, and a speed reduction mechanism 12 that is attached to an inner race 11 b of the bearing mechanism 11. . When the steering handle 2 is turned around the turning axis R by the driver, the traveling motor 10, the inner race 11b of the bearing mechanism 11 and the speed reduction mechanism 12 also turn around the turning axis R, and the drive wheels 7 are steered.

  Further, in this walkie forklift 100, the drive wheel suspension mechanism (drive wheel 7) is urged downward with respect to the vehicle body 3 between the outer race 11a of the bearing mechanism 11 constituting the drive wheel suspension mechanism and the frame 4. A spring member 15 is provided. Thereby, the axial weight of the drive wheel 7 is always kept constant regardless of the load of the load.

  In FIG. 7, the relationship between the load of the load 40 and the axial weight of each wheel 7, 8, 9 is shown. As shown in the figure, the axial weight of the caster wheel 8 and the load wheel 9 increases as the load 40 increases. However, the axial weight of the drive wheel 7 remains 400 kg even if the load 40 changes. is there. The axial weight of the drive wheel 7 can be arbitrarily set by the spring constant of the spring member 15. The spring constant is set so that the axial weight of the drive wheel 7 is sufficiently larger than the axial weight (200 kg) of the caster wheel 8 even at the maximum load (for example, 600 kg, see FIG. 7C). When the axial load of the caster wheel 8 approaches the axial load of the drive wheel 7 due to an increase in load, the drive wheel 7 slips, and the assist force by the travel motor 10 cannot be transmitted well to the road surface.

Japanese Patent Laid-Open No. 5-4586

  According to the conventional walkie forklift 100 described above, it is possible to reduce the steering force when transporting heavy objects by making the axle weight of the drive wheel 7 constant, but on the other hand, the axle weight at light load is necessary. There was a problem of becoming larger than that.

  More specifically, in the above-mentioned walkie forklift 100, since the axle load of the drive wheel 7 is determined based on the maximum load, the drive wheel at a light load (for example, no load condition shown in FIG. 7A). 7 had an unnecessarily large axle load. As a result, the wear of the drive wheels 7 increases, the driver's burden increases with an increase in steering force, the drive wheel suspension mechanism peripheral members (4, 11, 12, 13, 15 etc.) deteriorate early, and the driving resistance increases. Various problems such as an increase in battery consumption occurred.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a walkie forklift capable of reducing the axle load of a drive wheel at a light load while preventing the drive wheel from slipping. There is.

  In order to solve the above problems, a walkie forklift according to the present invention includes a drive wheel suspension mechanism that is vertically movable with respect to a vehicle body, and a drive that is suspended by the drive wheel suspension mechanism and is steered by a steering handle operation. A walkie forklift comprising a wheel and a spring member provided between the vehicle main body and the drive wheel suspension mechanism and biasing the drive wheel suspension mechanism downward with respect to the vehicle main body. A telescopic member provided between the vehicle body or between the end of the spring member and the drive wheel suspension mechanism, a slip detection unit for detecting the slip of the drive wheel, and when the slip is detected in the slip detection unit And a control unit that extends the telescopic member to increase the urging force of the spring member.

  In this configuration, since the spring member and the expansion / contraction member are connected in series between the drive wheel suspension mechanism and the vehicle main body, the axial weight of the drive wheel is determined by both the spring constant of the spring member and the expansion / contraction amount of the expansion / contraction member. Dependent. Further, in this configuration, when the slip of the drive wheel is detected, the elastic member is extended under the control of the control unit. Therefore, according to this configuration, even if a slip occurs, the expansion / contraction member extends, and the biasing force (axial weight of the drive wheel) by the spring member increases, so that the slip is eliminated. The spring constant of the spring member can be set low. That is, it is possible to reduce the axle load of the drive wheel at a light load while preventing slipping.

  Preferably, the control unit of the walkie forklift reduces the biasing force by the spring member by contracting the expansion and contraction member when the slip detection unit does not detect a slip for a certain period of time. According to this configuration, the shaft weight of the drive wheel can be kept at a small appropriate value so as not to slip.

  The telescopic member of the walkie forklift can be, for example, a hydraulic cylinder.

  If the expansion / contraction member is a hydraulic cylinder, a branch line branched from a hydraulic oil delivery line that sends hydraulic oil to the lift cylinder is connected to the hydraulic cylinder, and the shaft that opens and closes under the control of the control unit. A shaft weight reduction adjusting valve that opens and closes under the control of a control unit in a hydraulic oil recovery line for recovering hydraulic oil sent to the hydraulic cylinder through the shaft weight increase adjusting valve through the weight increase adjusting valve By interposing, the expansion and contraction of the elastic member can be realized with a relatively simple configuration.

  ADVANTAGE OF THE INVENTION According to this invention, the walkie forklift which can reduce the axial weight of the drive wheel at the time of light load can be provided, preventing the slip of a drive wheel.

It is the walkie forklift according to the present invention, (A) is a partial cross-sectional schematic view seen from the side, (B) is a partial cross-sectional schematic view seen from the front. It is a hydraulic circuit diagram of the walkie forklift according to the present invention. It is a flowchart which shows the axial load control of the walkie forklift which concerns on this invention. It is a schematic diagram which shows the relationship between the load of a load and the axial weight of each wheel of the walkie forklift which concerns on this invention. It is the partial cross section schematic diagram which looked at the walkie forklift which concerns on the modification of this invention from the front. It is the conventional walkie forklift, Comprising: (A) is the partial cross-section schematic diagram seen from the side surface, (B) is the partial cross-section schematic diagram seen from the front. It is a schematic diagram which shows the relationship between the load of a load and the axial weight of each wheel of the conventional walkie forklift.

  Hereinafter, preferred embodiments of a walkie forklift according to the present invention will be described with reference to the accompanying drawings.

  As shown in FIG. 1, a walkie forklift 1 according to the present invention includes a vehicle main body 3, a battery storage portion 5 that moves up and down as a lift cylinder 16 in the vehicle main body 3 expands and contracts, and a front of the battery storage portion 5. A pair of left and right forks 6 attached to the steering wheel 2 and a steering handle 2 attached to the upper part of the vehicle body 3 so as to be turnable are provided. A drive wheel 7 suspended by a drive wheel suspension mechanism and a pair of caster wheels 8 disposed on the left and right sides of the vehicle body 3 are provided at the lower portion of the vehicle body 3. A wheel 9 is provided. The own weight of the walkie forklift 1 and the load of the load loaded on the fork 6 are carried by the drive wheel 7, the caster wheel 8 and the load wheel 9.

  The drive wheel suspension mechanism includes a bearing mechanism 11 that can be moved up and down with respect to the frame 4 of the vehicle body 3 by a link mechanism 13, and a speed reduction mechanism 12 that is attached to an inner race 11 b of the bearing mechanism 11. . When the steering handle 2 is turned around the turning axis R by the driver, the traveling motor 10, the inner race 11b of the bearing mechanism 11 and the speed reduction mechanism 12 also turn around the turning axis R, and the drive wheels 7 are steered.

  The walkie forklift 1 is provided with a shaft weight adjusting cylinder 14 and a spring member 15 connected in series between an outer race 11a of a bearing mechanism 11 and a frame 4 constituting a drive wheel suspension mechanism. The axle load adjusting cylinder 14 is a hydraulic cylinder corresponding to the telescopic member of the present invention. As shown in FIG. 1, the bottom side of the axle load adjustment cylinder 14 is connected to the frame 4, the distal end of the axle load adjustment cylinder 14 is connected to the upper end portion of the spring member 15, and the lower end portion of the spring member 15 is the bearing mechanism 11. This is merely an example, and various modifications are conceivable. For example, as shown in FIG. 5, the bottom side of the axle load adjustment cylinder 14 is connected to the outer race 11 a of the bearing mechanism 11, the tip of the axle load adjustment cylinder 14 is connected to the lower end of the spring member 15, and the spring member 15 The upper end may be connected to the frame 4.

  The spring member 15 urges the drive wheel suspension mechanism (drive wheel 7) downward with respect to the vehicle body 3 with an urging force determined by the spring constant.

  The axle load adjusting cylinder 14 is controlled to extend when the drive wheel 7 slips, and to contract when the drive wheel 7 does not slip for a certain time. The control of the axle load adjustment cylinder 14 will be described in detail later.

  In order to realize the telescopic operation of the axle load adjusting cylinder 14, the walkie forklift 1 according to the present invention includes a hydraulic circuit 20, a slip detection unit 31, and a control unit 32. The slip detection unit 31 detects, for example, whether or not the drive wheel 7 is slipping based on the difference between the command value for the travel motor 10 and the output value of the rotation speed sensor provided in the bearing mechanism 11, and the detection result Output a signal according to. The control unit 32 includes a CPU and a computer program.

  As shown in FIG. 2, the hydraulic circuit 20 sends the hydraulic oil in the tank 21 to the bottom chamber of the lift cylinder 16 via the hydraulic oil delivery line 27 when raising the tank 21 for storing the hydraulic oil and the fork 6. When the fork 6 is lowered, the hydraulic pump 22, the hydraulic oil recovery line 28 for returning the hydraulic oil of the lift cylinder 16 to the tank 21, the fork lowering control valve 24, and the hydraulic oil delivery line for preventing the hydraulic oil from flowing back 27 and a check valve 23 provided in the middle.

  In addition, the hydraulic circuit 20 of the walkie forklift 1 according to the present invention operates to recover the branch line 29 branched from the hydraulic oil delivery line 27 and the hydraulic oil sent to the axle load adjustment cylinder 14 through the branch line 29. An oil recovery line 30 is provided.

  As shown in the figure, the start end of the branch line 29 is connected to the hydraulic oil delivery line 27 (more specifically, between the check valve 23 and the lift cylinder 16), and the end of the branch line 29 is the bottom of the axle load adjusting cylinder 14. Connected to the room. The branch line 29 is provided with an electromagnetic valve (hereinafter referred to as an axial load increase adjusting valve 25) that opens and closes under the control of the control unit 32. When the shaft load increase adjusting valve 25 is opened by the control unit 32, hydraulic oil is sent to the bottom chamber of the shaft load adjusting cylinder 14 through the branch line 29, and the shaft load adjusting cylinder 14 is extended.

  The hydraulic oil recovery line 30 is a line for recovering hydraulic oil sent to the bottom chamber of the axle load adjustment cylinder 14 through the branch line 29 and the axle load increase adjustment valve 25. The hydraulic oil recovery line 30 is provided with an electromagnetic valve (hereinafter referred to as a shaft weight reduction adjusting valve 26) that opens and closes under the control of the control unit 32. When the shaft load reduction adjusting valve 26 is opened by the control unit 32, the hydraulic oil in the bottom chamber of the shaft load adjustment cylinder 14 is collected in the tank 21 through the hydraulic oil collection line 30, and the shaft load adjustment cylinder 14 is contracted.

  When the axle load adjustment cylinder 14 expands and contracts under the control of the control unit 32, the urging force by the spring member 15 increases and decreases according to the expansion and contraction amount, and the axle load of the drive wheel 7 increases and decreases. In other words, the control unit 32 can adjust the shaft weight of the drive wheel 7 by opening and closing the shaft weight increase adjustment valve 25 or the shaft weight decrease adjustment valve 26. The expansion / contraction amount (shaft weight adjustment amount) of the shaft weight adjustment cylinder 14 is the amount of hydraulic fluid flowing through the shaft weight increase adjustment valve 25 or the shaft weight decrease adjustment valve 26, that is, the time during which the valves 25 and 26 are open. It depends on.

  Further, as shown in FIG. 2, the shaft load increase adjustment valve 25 and the shaft load decrease adjustment valve 26 are normally closed, so that the hydraulic pressure of the shaft load adjustment cylinder 14 is kept constant. Therefore, unless the valves 25 and 26 are controlled to be opened and closed by the control unit 32, the axle load adjusting cylinder 14 does not expand and contract freely, and the axle load of the drive wheel 7 does not change.

  FIG. 3 is a flowchart illustrating an example of adjusting the axial load by the control unit 32. As shown in the figure, when the accelerator is turned on in step S1, the control unit 32 determines whether or not the accelerator is continuously turned on after turning on the travel motor 10 (step S2) (step S3). . If it is determined that the accelerator is OFF, the traveling motor 10 is turned OFF (step S8), and the axle load adjustment flow ends.

  When it is determined in step S3 that the accelerator is ON, the control unit 32 determines whether or not the drive wheel 7 slips based on the signal from the slip detection unit 31 (step S4). When it is determined that there is a slip, the control unit 32 opens the axle load increase adjusting valve 25 for a predetermined time (step S5). As a result, the hydraulic oil is sent to the shaft weight adjusting cylinder 14 to increase the shaft weight of the drive wheel 7, thereby eliminating the slip. If the slip does not disappear even if the shaft weight increases, the shaft weight increase adjusting valve 25 is opened again for a predetermined time in the next step S5, and the shaft weight further increases. That is, by repeatedly executing Steps S3 to S5, the shaft weight of the drive wheel 7 is increased to the extent that it does not slip.

  If it is determined in step S4 that there is no slip, the control unit 32 determines whether or not a slip has occurred for a certain time (step S6). When it is determined that no slip has occurred for a certain period of time, the control unit 32 opens the axle load reduction adjusting valve 26 for a certain period of time (step S7). As a result, the hydraulic oil in the axle load adjusting cylinder 14 is collected in the tank 21 and the axle load of the drive wheel 7 is reduced. Steps S3, S4, S6, and S7 are repeatedly executed until it is determined in step S4 that the slip is present, and the axial weight of the drive wheel 7 gradually decreases.

  The time during which the shaft weight increase adjusting valve 25 is kept open (step S5) and the time when the shaft weight decrease adjusting valve 26 is kept open (step S7) are not particularly limited in the present invention, but the valves 25, 26 are kept open for a long time. Care should be taken because the axle load of the drive wheel 7 changes suddenly and the steering feel changes. The determination in step S6 is performed in a state in which the heavy load 40 is loaded so that the axial weight of the caster wheel 8 approaches the axial weight of the drive wheel 7 and easily slips. For example, the friction coefficient is high. This is to prevent the axle load of the drive wheel 7 from decreasing when the vehicle travels temporarily on the road surface.

  As a result, according to the walkie forklift 1 according to the present invention, when traveling while loading a load, it is possible to increase the axial weight of the drive wheel 7 to the extent that it does not slip by repeatedly executing step S5. Further, when traveling with the cargo unloaded, the axial load of the drive wheel 7 can be reduced within a range where slip does not occur by repeatedly executing step S7. That is, according to the walkie forklift 1 according to the present invention, the shaft weight of the drive wheel 7 can be kept at a small appropriate value so as not to slip.

FIG. 4 is a diagram showing the relationship between the load of the load 40 loaded on the fork 6 and the appropriate axial weight of the drive wheel 7. As shown in the figure, when the load of the load 40 is 0 kg (no load), 400 kg, and 600 kg, the length of the axle load adjusting cylinder 14 is L ₀ , L ₄₀₀ , and L ₆₀₀ , respectively. The axle loads are 250 kg, 300 kg, and 400 kg, respectively.

  As described above, in the walkie forklift 1 according to the present invention, the shaft weight of the drive wheel 7 depends on both the spring constant of the spring member 15 and the amount of expansion / contraction of the shaft weight adjusting cylinder 14. The axle load adjusting cylinder 14 is controlled to extend when the drive wheel 7 slips, and to contract when the drive wheel 7 does not slip for a certain time. Therefore, according to the walkie forklift 1 according to the present invention, it is possible to prevent the drive wheel 7 from slipping, and by setting the spring constant of the spring member to be low with reference to the light load, The axial weight of the drive wheel 7 can be reduced.

  In addition, said structure is only an example, Comprising: This invention is not limited to said structure.

  For example, in the above-mentioned walkie forklift 1, the axle load adjustment cylinder 14 (hydraulic cylinder) is used as an expansion / contraction member that expands and contracts according to the load of the load 40, but it can be changed to another member that can perform the same expansion / contraction operation. .

  Various modifications can be considered for the manner of attaching the axial load adjusting cylinder 14 and the spring member 15. In short, when the axle load adjusting cylinder 14 expands and contracts, the position of one end of the spring member 15 moves up and down, and the downward biasing force of the spring member 15 acting on the drive wheel suspension mechanism (drive wheel 7) changes. It only has to come to do.

  In the hydraulic circuit 20 shown in FIG. 2, the hydraulic oil sent from the hydraulic pump 22 for the lift cylinder 16 is diverted to achieve expansion and contraction of the axle load adjustment cylinder 14 with a relatively simple configuration. Further, a dedicated hydraulic pump for sending hydraulic oil to the axle load adjusting cylinder 14 may be further provided.

DESCRIPTION OF SYMBOLS 1 Walkie forklift 2 Steering handle 3 Vehicle main body 4 Frame 5 Battery storage part 6 Fork 7 Drive wheel 8 Caster wheel 9 Road wheel 10 Traveling motor 11 Bearing mechanism 12 Deceleration mechanism 13 Link mechanism 14 Axial load adjustment cylinder 15 Spring member 16 Lift cylinder 20 Hydraulic circuit 21 Tank 22 Hydraulic pump 23 Check valve 24 Fork lowering control valve 25 Shaft weight increase adjustment valve 26 Shaft weight decrease adjustment valve 27 Hydraulic oil delivery line 28 Hydraulic oil recovery line 29 Branch line 30 Hydraulic oil recovery line 31 Slip detection unit 32 Control unit 40

Claims (5)

A drive wheel suspension mechanism provided to be movable up and down with respect to the vehicle body, a drive wheel suspended by the drive wheel suspension mechanism and steered by a steering handle operation, and between the vehicle body and the drive wheel suspension mechanism A walkie forklift provided with a spring member that biases the drive wheel suspension mechanism downward with respect to the vehicle body,
A telescopic member provided between the end of the spring member and the vehicle body, or between the end of the spring member and the drive wheel suspension mechanism,
A slip detector for detecting slip of the drive wheel;
When the slip is detected in the slip detection unit, the control unit extends the expansion member and increases the urging force by the spring member;
A walkie forklift characterized by comprising   2. The walkie forklift according to claim 1, wherein when the slip is not detected for a certain period of time in the slip detection unit, the control unit contracts the telescopic member to reduce the urging force of the spring member.   The walkie forklift according to claim 1 or 2, wherein the telescopic member is a hydraulic cylinder.   The hydraulic cylinder is connected to a branch line branched from a hydraulic oil delivery line that sends hydraulic oil to the lift cylinder. The branch line is provided with a shaft load increase adjusting valve that opens and closes under the control of the control unit. The walkie forklift according to claim 3, wherein:   A hydraulic oil recovery line for recovering hydraulic oil sent to the hydraulic cylinder through the axial load increase adjustment valve is provided, and the hydraulic oil recovery line has an axial load decrease that opens and closes under the control of the control unit. 5. The walkie forklift according to claim 4, wherein a regulating valve is interposed.

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